Fluidized solids transfer



Jan. 2, 1951 v. vooRHEEs 2,536,402

FLUIDIZED SOLIDS TRNSFER Filed OGL 15,-1945 2 SheetS-Sheet 1 In venor-- Vander-veer' Voorhees Jan. 2, 1951 v. voQRHEL-:s

FLUIDIZED SOLIDS TRANSFER 2 Sheets-Sheet 2 Filed OCT.. 13. 1945 LOxOBMQ ANN m l Patented 1951 2,536,402 l FLUIDIZED SOLIDS TRANSFER Vanderveen' Voorhees, Homewood, Ill., assignor to Standard Oil Company, Chicago, lll., a corporation of Indiana Application October 13, 1945. Serial No. 622,229

(Cl. 3oz-36) 'z claims. l

This invention relates to a method and apparatus for transferring powdered solids from a region tial back pressure, without diiliculty lrom'erosion, abrasion or attrition.

In conducting catalytic reactions it is often desirable to operate the catalytic reaction chamber at substantial pressures of the order of 50 p. s. i. to 500 p. s. i. In processes of hydroforming hydrocarbons, naphtha, etc., it is frequently desirable to operate at pressures oi 100 to 400 p. s. i. in the presence of hydrogen. Heretofore it has been necessary to conduct these processes with fixed bed catalysts. An object of my invention is to provide a pump for charging finely divided catalysts to reactions of this kind and thereby obtain the advantages of iluidized catalyst operation, advantages such as continuous operation and uniform temperature control.

Another object of my invention is to provide a pump for transferring powdered solids against substantial pressure which will have a high capacity for a relatively small unit size and which will be thoroughly reliable and continuous in action and easily controllable with respect to starting, stopping and throughput. This application is a continuation-in-part of my application Serial 596.583, filed May 29, 1945, now 4Patent No. 2,495,152, issued January 17, 1950.

The invention is illustrated by drawings in which Figure 1 shows the body and impeller of a suitable design of powdered solids pump but without means for controlling the flow of solids thru the Pump;

Figure 2 illustrates a similar body design but with a different type o1' rotating element or bowl provided with pneumatic dow-control means;

Figures 3 and 4 illustrate pumps with the same bowl construction as in Figure 1 but equipped with different arrangements of pneumatic means for controlling the ow of solids from the periphery of the bowl.

The problem of transferring fluidized solids such as wheat flour, cornstarch, Portland cement, powdered lime, powdered coal. and powdered catalysts typified by Super Filtrol clays, synthetic hydrocarbon conversion catalysts such as silicaalumina, molybdenum oxide on alumina, microspherical silica gel, etc., presents numerous diillculties not encountered in the transfer of true liquids and gases. Thus, although the finely di vided solids may be fluidized by aeration and conveyed thru pipes much in the same way as is done with liquids. these uidized streams are substantially impossible topump with the usual pumping equipment employed for liquids. for the reason that deaeration may occur at any time, for example by shutting down or under the innuence of centrifugal and gravitational forces, thereby causing the iluidized solids to collect as an immobile mass in the apparatus. Furthermore, the handling of such iluidized solids in centrifugal equipment such as the ordinary centrifugal pump where the bowl is moving at high velocity commonly results in severe erosion of the moving parts. In the case of screw-type and plungertype pumps, abrasion results from the impossi-v bility of lubrication and the abrasive character of most of the iiuidized solids being handled.

Previous attempts to handle fluidized solids in centrifugal pumps have not been successful for these reasons. Thus, in U. S. Patent 1,937,040 a centrifugal pump design is described employing flow-control means subject to extreme abrasive action resulting in high upkeep costs, non-uniform operations, and damage to the granular structure of the iiuidized solids being handled. According to my invention. the solids are transferred against higher pressure by centrifugal action using an entirely new principle wherein the iiuidized solids are substantially deaerated and compacted in the rotating member or bowl of the pump and then reaerated at the periphery of the bowl to restore their fluid characteristics and a1- low them to ow from the bowl, the rate of flow being controllable by the manner and extent of reaeration. As a result the pump I have provided may be used for transferring solids in one or more i stages from low pressures to high pressures. The

action is dependable and continuous and easily controlled with respect to throughput. The invention will be better understood by referring to the drawings.

In Figure 1. rotating element B carried on shaft 9 running in bearing I0 is positioned 'within pump housing II Induction tube I2 for catalyst or other powdered solids extends thru hollow shait 9 into the central portion of the bowl 8. Solids are permitted to accumulate in the lower part of pump case I I and are maintained uidized by the introduction of aeration gas uch as air at I3 and I 4. Additional gas may be injected at I5 to maintain the pressure within case Il at the desired point for expelling uidized solids from the outlet I6. This drawing shows no means for controlling the flow of solids from the periphery of the rotating bowl 8. It is therefore substantially inoperative, or only critically operative. If the supply of solids to the pumpthru induction tube I2 is maintained uninterrupted, and if the pressure differential within the pump is relatively low there is a critical condition at which the pump may be made to function, the solids remaining aerated and fluid within the bowl 8. Deaeration, is very likely to take place within the bowl, howlever, with the result that the bowl rapidly becomes filled or plugged with deaerated solids packed tightly therein and incapable of transmitting pressure to the outlet of the bowl and escaping therefrom. 4

The critical operating characteristic is overcome by the design shown in Figure 2, wherein the bowl consists of one or more pairs of dynamically balanced legs I1 arranged as the spokes of a wheel. These may be constructed of short pipes with return bends at the periphery, the

inner ends being welded into a hollow hub into which the catalyst or other fiuidized solids is admitted by induction tube I8. From the hub the catalyst is thrown outwardly by the centrifugal action of the rapidly whirlying assembly or wheel and the catalyst accumulates in the return bends I9 where it is deaerated, effectively preventing flow of catalyst thru the return bend to the outlet 20 thereof, as a result of the substantial impossibility of transmitting fluid pressure from the leg I1 to the outlet 20 facing radially inward. This condition forms an effective seal against back pressure within the chamber 2I. Furthermore the rotating leg I1, lled with compacted solids, exerts suilcient centrifugal force in the direction of outlet 2Il to more than balance the pressure in housing 2|, the density of the compacted catalyst, the length of leg I1, andthe speed of rotation being designed sufficient to more thanovercome the pressure for which the pump is employed. v .A

In order to induce 'cataly'stflowthru the apparatus and regulate-it, lthere is provided at the bottom-of each return bendv I9 a gasA inlet; 22` supplied by gas, e. g .air -itroducedthruline 23 v.

and-distributor 24, IIhe injection of air. or gas at points 22 effects the V aeration 4of'thesolids in the .y

returnbends I9, thereby removing the-catalyst block therein and permitting the flow of catalyst thruvlegs I1, when the catalyst in the leg/s I1 vis no longer supported by the'block fofcatalyst in return bends I9. Rate of flowl may be increased or decreased by regulating the rate of air lintroduction in line..23'.` The fiuidized catalyst leaving outlets 28 accumulates in fiuidized condition in thebottrn of chamber 2I where itis maintained4 fiuidized by additional aeration-lgas-introducedby lines 2 5 and 25a. The fiuidized' catalyst is with;

drawn thru outlet ,26. wh'eregitma'y join astream I' One of the chf, acteristics of'thjs centrifugal pump, designvforpowdered solids isthe stationary induction tube I8 leading "the fiuidized catalyst into the bowl.--An annular space surrounding the induction-'tube within the hollow shaft 9 permits the egress of gas separated from the solids in the bowl without blocking of the inlet. Furthermore, by maintaining the induction tube I8 stationary, there is 'no centrifugal deaeration action exerted upon the catalyst stream until after it has entered the bowl.

Referring now to Figure 3, aeration and refluidizing of lthe compact catalyst massed in the periphery of bowl 28 is effected by directing one or more blasts or jets of air against the surface of the compacted catalyst accumulated in channel 29. For this purpose, air or other gas is introduced by line 38 leading to distributor 3I. Nozzle 32 directs the air against the catalyst which normally prevents the flow of catalyst thru the pump and escape of gas backward thru the impeller.

Figure 4 illustrates an apparatus which embodies the same principle as that in Figure 3 with respectto the application of a gas stream to the surface of the catalyst in channel 33. However, in the design shown in Figure 4, the gas which impinges upon the surface of the catalyst is derived from the rotation of the bowl itself in the following manner: The bottom of the bowl, comprised of plate 34, is equipped with fins or vanes 35. The movement of air across the surface of the plate under the influence of the rapidly rotating fins is confined by baille plate 38 which is a circular plate corresponding substantially in diameter to the bowl. At the periphery of plate 36 a rim 31 acts as a loose seal against the bottom of the bowl when the plate 36 is moved in an upward direction. The position of the plate is controlled by bearing 38 vertically slidable on shaft 39 by the action of control shaft 48 and arm 4I. The shaft 40 passes thru a packing gland, not shown, in the wall of the pump chamber to an external handwheel, crank, or other controlling device, not shown. Opening of the peripheral orifices by lowering plate 36 results in a strong draft or blast of gases against the surface of the compacted catalyst in vchannel 33, thereby sweeping the compacted catalyst out of the channel and Yinto the lower part of the pump chamber where it is maintained in fiuidized condition until withdrawn from the outlet 42.. Automaticcatalyst flow control may be achieved by means of a float, not shown, supported in the dense catalyst phase within the pump chamber and connected to the arm 4I so that the aeration gas supplied to channel 33 is cut off as the oat rises witli`"t-he"level of the catalyst body 43. Various modifications of my catalystl pump may be" employed without .departing from the basic `principles thereof.` Thus, instead of employing stationary. induction pipe I2, I may substitute al stationary helical feeder impelling catal prefer that the area of a co-axial cylindrical section of the bowl increase gradually toward the periphery in order to facilitate the flow of compacted solids therethru. An increase of 2 to 25 per cent in the cylindrical cross-sectional area per foot of radius from the center to the periphery issatisfactory. Y

l In case the amount of gas employed for refluidizing the catalyst at the periphery of the bowl be greater than that required for expelling the catalyst from the pump body into the outlet line, excess gas may be withdrawn thru a suitable excess-pressure valve, for example `valve 44 in Figure 3.

The design of Figure 4 employing no outside air 'pressure for reaerating the catalyst has the advantage of reduced air requirement over the other designs shown. Various modifications of the internal fan principle may be employed, for example, the plate 38 may be xed to the bowl with blades 35 constituting a permanent fan arrangement having a central gas inlet thru plate 36 which may be controlled by a cover plate actuated by arm 4| to allow more or less air to enter the suction of the fan.

In any of the designs, the speed of rotation of the bowl is suitably about 500 to 4000 R. P. M., although higher speeds may be used. Because of the relatively high density of the compacted solids in the bowl. it is not necessary to employ such high speeds as in the case of aerated solids. Thus, the density of the solids when compact will lusually lie between 1 and 2 wlth'metal oxides,

clays. etc. The speed of rotation should be suillcient to provide centrifugal pressure in excess of the back pressure acting on the bowl at the periphery.

Erosion of the bowl is not serious because of a relatively small rate of motion of the compacted catalyst therethru. The bowl 28 is preferably constructed with radial or spiral vans 45 to ass-st in imparting to the catalyst the reouired angular velocity. Smooth operation is facilitated by supplying, thru the catalyst induction tube I2, suilicient excess of fluidized solids over the requirement of the pump to provide a reverse flow of iiuidized solids thru the annular space 4B between the induction tube I2 and the hollow shaft 9, the rejected fluidized solids feed being collected by means not shown and recharged to the pump.

A suitable dense fluidized solids phase for use in this pump may have a densitv of about to 'l5 pounds per cubic foot. In the case of hydrocarbon conversion catalysts such as Super Filtrol. powdered silica-alumina, etc., having a particle size of about to 300 microns, corresponding roughly to to 400 mesh. the densityy of the fluidized suspension may be about 25 to 40 pounds per cubic foot. The deaerated solids in this case have a density7 of 55 pounds per cubic foot and upwards, e. g. to 100 pounds per cubic foot. The deaerated or compacted condition of tine solids is also characterized by a rigid or semirigid structure which fails to ow freely under the influence of gravity.

Where it is desired to pump heavier substances such as fluidized iron catalyst, considerably higher densities will be encountered, requiring a much smaller centrifugal bowl for operating against the same pressure. The pumping oi' fluidized iron and fluidized cobalt catalysts is sometimes required in the monoxide process (Fischer process) where carbon monoxide and hydrogen are converted into liquid hydrocarbons bv contact with these catalysts in fluidized solid form.

In the cracking of oils such as gas oil, where the catalyst must be frequently regenerated by recycling thru a reactor and regenerator system, the repeated handling of the catalyst results in more or less breakdown of the particles by attrition. High attrition rates result in loss of fines and impose the requirement of special recovery means, such as electrical precipltators. By the use of my catalyst pump, recycling of catalyst can be maintained in such systems with a minimum of attrition and a substantial pressure differential can be maintained between the retor and the regenerator.

Having thus described my invention, what I claim is:

l. An apparatus for transferring finely divided solids from a low pressure supply of fluidized solids to a zone of higher pressure which comprises rotatable means positioned within said zone of higher pressure for rotating a compacted mass oi' said solids, a conduit leading from said supply to the center of rotation of said mass for conducting aerated iluidized solids thereto, an opening at the periphery of said rotatable means for discharging solids from said mass, peripheral baffle means associated with said opening for retaining a body of compacted solids against said opening to prevent movement of solids thru said opening during rotation of said rotatable means, and means for introducing an aerating gas into said body to control the flow of solids from said `rotating mass thru said opening by iluidization of the solids in said body obstructing said opening.

2. A fluidized solids pump comprising a gastight housing, an outlet for solids at a low point therein, a rotatable hollow impeller member within said housing at the upper part thereof, a hollow shaft extending thru the wall of said housing and connecting with said impeller member, means for supplying powdered solids thru said shaft to the interior of said impeller member, an opening near the periphery of said impeller member leading outwardly in a radial direction from the interior thereof, a baille opposite said opening and radially outward therefrom providing suiicient peripheral support to maintain a body of compacted solids against said opening and prevent flow of solids therethru while said impeller member is rotating at substantial speed, and controllable means for introducing an aerating gas into said body oi' compacted solids to iiuidize them and thereby permit solids to pass from the interior of said impeller member thru said opening into said housing.

3. The apparatus of claim 2 wherein said impeller is circular in form and said baille is comprised of a channel at the periphery thereof.

4. The apparatus of claim 2 wherein said impeller is a radially positioned tube and said baille is formed by a return bend at the outer end of said tube.

5. The apparatus of claim 2 wherein the area of a co-axial cylindrical section thru said impeller member increases from the center to the periphery at the rate of about 2 to 25 per cent per foot of radius.

6. The apparatus of claim 1 wherein the means for introducing an aerating gas into the said body comprises a jet positioned to direct a high velocity stream of aeration gas against the surface of said solids, and means for supplying aeration gas under pressure to said jet.

'7. The apparatus of claim 1 wherein the means for introducing an aerating gas into said body comprises a plurality of radial fins fixed to the bottom of said rotatable means, and an annular baffle plate spaced below the bottom o! said rotatable means, the periphery of said annular baille plate terminating adjacent said peripheral baille means.

VANDERVEER VOORHEES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1937,040 Vogel-Jorgensen Nov. 28, 1933 2,360,464 Arveson Oct. 17, 1944 

1. AN APPARATUS FOR TRANSFERRING FINELY DIVIDED SOLIDS FROM A LOW PRESSURE SUPPLY OF FLUIDIZED SOLIDS TO A ZONE OF HIGHER PRESSURE WHICH COMPRISES ROTATABLE MEANS POSITIONED WITHIN SAID ZONE OF HIGHER PRESSURE FOR ROTATING A CONNECTED MASS OF SAID SOLIDS, A CONDUIT LEADING FROM SAID SUPPLY TO THE CENTER OF ROTATION OF SAID MASS FOR CONDUCTING AERATED FLUIDIZED SOLIDS THERETO, AN OPENING AT THE PERIPHERY OF SAID ROTATABLE MEANS FOR DISCHARGING SOLIDS FROM SAID MASS, PERIPHERAL BAFFLE MEANS ASSOCIATED WITH SAID OPENING FOR RETAINING A BODY OF COMPACTED SOLIDS AGAINST SAID OPENING TO PREVENT MOVEMENT OF SOLIDS THRU SAID OPENING DURING ROTATION OF SAID ROTATABLE MEANS, AND MEANS FOR INTRODUCING AN AERATING GAS INTO SAID BODY TO CONTROL THE FLOW OF SOLIDS FROM SAID ROTATING MASS THRU SAID OPENING BY FLUIDIZATION OF THE SOLIDS IN SAID BODY OBSTRUCTING SAID OPENING. 